Astyanax jordanensis (Ostariophysi: Characidae), a new species from the rio Iguaçu basin, Paraná, Brazil

Astyanax jordanensis, new species, is described from the rio Jacu and rio das Torres, both tributaries to the lower rio Jordão, in the rio Iguaçu basin, Paraná, Brazil. The new species is a member of the A. scabripinnis species complex. Astyanax jordanensis differs from its congeners by several meristic and morphometric characters. Mature males possess bony hooks in the dorsal, pectoral, pelvic, and anal fins, and mature females have a few small bony hooks on the first rays of the anal fin. The presence of these bony hooks in females and the endemism of the ichthyofauna in the rio Jordão are discussed.

The ichthyofauna of the rio Iguaçu basin demonstrates a high degree of endemicity as a consequence of the Iguaçu Falls situated near the mouth of that river that serves as an effective barrier for fish dispersal.Six species of Astyanax occur in that drainage: A. altiparanae Garutti & Britski, 2000;A. gymnogenys Eigenmann, 1911;A. ita Almirón, Azpelicueta & Casciotta, 2002;A. leonidas Azpelicueta, Casciotta & Almirón, 2002;A. totae Haluch &Abilhoa, 2005 andA. varzeae Abilhoa &Duboc, 2007.Except for A. altiparanae and A. leonidas, all remaining species are apparently endemic to the rio Iguaçu basin.Collecting efforts throughout the rio Iguaçu basin by the Núcleo de Pesquisas em Limnologia, Ictiologia e Aqüicultura (Nupélia) demonstrated that the tributary rio Jordão has its own endemic fish fauna including the species described as new in this paper.

Material and Methods
Counts and measurements were taken on the left side of specimens whenever possible, according to Fink & Weitzman (1974), with the exception of the number of scale rows below the lateral line which followed Bertaco & Malabarba (2001).Measurements were taken point to point with a caliper to the nearest 0.1 mm.Measurements are expressed as percents of standard length (SL), except for subunits of the head, that are recorded as percents of head length (HL).Values in parentheses indicate the number of specimens with a particular count, and an asterisk indicates value of the holotype.
Osteological observations and counts of fin rays, pterygiophores, vertebrae, supraneurals, and procurrent rays were done on radiographed and cleared and stained (c&s) specimens prepared according to Taylor & Van Dyke (1985).
Counts of ribs and gill rakers were taken only in c&s specimens.Vertebral counts included the four vertebrae of the Weberian apparatus, with the terminal compound centrum counted as a single element.Sexes of twenty specimens were determined by direct observation of the gonads, with the remaining specimens sexed based on sexual dimorphic characters.Lower and upper jaws of one c&s specimen were prepared for Scanning Electronic Microscopy (SEM) analysis.Institutional abbreviations are as listed at http:// research.calacademy.org/research/ichthyology/catalog/abtabr.html,with addition of Copel (Companhia Paranaense de Energia).

Astyanax jordanensis, new species
Figs.  1. Body compressed and elongate; greatest body depth usually located anterior to dorsal-fin origin.Dorsal profile of body convex from snout to dorsal-fin origin, nearly straight along dorsal-fin base, straight or slightly concave from last dorsal-fin ray to adipose fin.Ventral profile of body convex from mouth to anal-fin origin, nearly straight along anal-fin base.Caudal peduncle elongate and nearly straight to slightly concave along both dorsal and ventral margins.Head small.Mouth terminal, lower jaw slightly shorter than upper jaw.Maxilla extending posteriorly to vertical through middle of orbit, slightly curved, and forming angle of about 45 degrees relative to longitudinal body axis.
Premaxilla with two teeth rows, outer row with 3(7), 4*(28), or 5(2) teeth with three to five cusps.Inner premaxillary row with 5*(40) teeth, symphysial teeth with four cusps, second and third teeth with four to seven cusps and two posterior most teeth smaller with three to five cusps.Maxilla with 1*(25) or 2( 14) teeth with three cusps.Dentary with the four anterior most teeth larger, with five to seven cusps.Large teeth of dentary followed by six to eight smaller teeth with one to three cusps, gradually decreasing in size.All teeth with central cusp longer than lateral cusps (Fig. 2).Gill rakers on dorsal limb of outer gill arch 6(3), and on ventral limb 10(2) or 11(1).
Color in alcohol.Dorsal portion of head and body densely dark brown; dorsolateral portions of head and body brownish and lighter ventrally.Body with broad, blackish midlateral band from humeral region to caudal peduncle.Midlateral band expanded dorsally and ventrally into a dark lozenge shaped spot on caudal peduncle.Single, brown, narrow, sometimes inconspicuous vertically elongate humeral spot.Dorsal portion of spot slightly wider than ventral.Ventral limit of spot over first to second scale below lateral line and dorsal limit about two to three horizontal series of scales above lateral line.Fins with scattered dark chromatophores, mainly over distal third; pigmentation more obvious on median fins.Caudal fin with a faint dark pigmentation on middle rays.
Sexual dimorphism.Males of Astyanax jordanensis posses bony hooks on the dorsal-, pectoral-, pelvic-, and anal-fin rays, albeit with hooks less evident on the dorsal fin.Males and females also slightly differ in the proportions of the dorsal, pectoral, and pelvic fins (Table 1) and in the anal-fin shape, which is concave in females and nearly straight in males (Fig. 1).Mature females reach larger body sizes than mature males (44.3-75.7 mm vs. 34.2-47.7 mm SL, respectively).Twenty one mature female paratypes have a few small bony hooks on the last unbranched ray and anterior branched anal-fin rays, a character unusual in characids (see discussion for more details).Gill glands were not found in either males or females.
Distribution.All specimens were collected in the middle and upper portions of rio Jacu and rio das Torres in the lower portions of the rio Jordão drainage, lower rio Iguaçu basin, Paraná, Brazil (Fig. 3).
Etymology.The specific name jordanensis is in reference to the drainage from where the species is described, the rio Jordão, a tributary to the rio Iguaçu basin.An adjective.
Ecological notes.Stomach contents of four paratypes included aquatic insects (Epemeroptera; Hemiptera: an adult of Gerridae; Diptera: pupa, and larvae of Ceratopogonidae), terrestrial insects (adults of Diptera; Hymenoptera; Lepidoptera; and Coleoptera), and plant fragments (fruits of Gramineae; sporophytes and leaves of the Bryophyta).

Discussion
The diagnosis of Astyanax jordanensis was constructed comparing members of the A. scabripinnis species complex which fits all the characters delimited by Bertaco & Lucena (2006).The species A. epiagos and A. jacobinae, recently Fig. 3. Partial map of South America showing the distribution of Astyanax jordanensis (dot).The symbol represents more than one lot and locality.described and included in this complex by Zanata & Camelier (2008), were not compared.To our understanding, they do not fit all the characters delimited for that complex since they lack the midlateral dark body stripe.However, other characters also differentiate A. jordanensis from these species, including a single series of five to seven scales covering base of anterior anal-fin rays and a reduced area of skin between infraorbitals and preopercle (vs.scales absent over anal-fin base and a broad area of skin in A. epiagos), and 13-17 branched anal-fin rays and dentary teeth abruptly decreasing in size after the fourth tooth (vs.19-22 rays and teeth gradually decreasing in size posteriorly in A. jacobinae).
The high degree of endemism of the ichthyofauna of rio Iguaçu is likely a consequence of the Iguaçu falls that are situated close to the mouth of the river into the rio Paraná (Garavello et al., 1997).Ingenito et al. (2004) recorded 41 fish species in the upper rio Iguaçu basin, of which eight were considered endemic.In the lower rio Iguaçu basin, Baumgartner et al. (2006) also recorded 41 fish species, but considered 19 endemic when compared to the upper portions of the basin, suggesting that there are regions of endemicity even within the rio Iguaçu basin.That hypothesis also applies to the rio Jordão drainage, from where six endemic species have already been described: Cnesterodon omorgmatos Lucinda & Garavello, 2001; Jenynsia diphyes Lucinda, Ghedotti & Graça, 2006;Trichomycterus crassicaudatus Wosiacki & de Pinna, 2008;T. igobi Wosiacki & de Pinna, 2008;T. plumbeus Wosiacki & Garavello, 2004and T. taroba Wosiacki & Garavello, 2004. Lucinda et al. (2006) attribute this endemism to a 15 meter high waterfall that was close to the mouth of the rio Jordão, and which may restrict fish dispersal between the rio Jordão drainage and the remaining portions of the rio Iguaçu basin.This waterfall, the Vaca Branca, is now submerged under a reservoir.Astyanax jordanensis similarly seems to be endemic to this drainage.
Mature males of Astyanax jordanensis possess bony hooks on all fin rays except the caudal fin.Presence, shape, and number of hooks in different fins have been considered synapomorphic for several groups in the Characidae (Malabarba & Weitzman, 2003), but with hooks usually found only on the anal and pelvic fins, and sometimes on the caudal fin of males.Recently, Gonçalves et al. (2005) observed a positive correlation between the mean gonadossomatic index and the number of anal-fin rays bearing hooks in mature males of Aphyocharax anisitsi Eigenmann & Kennedy, 1903.They suggested that those hooks develop with testis maturation, and once developed they are retained by the males.
It is noteworthy that most of examined mature females of A. jordanensis also posses a few small bony hooks on the last unbranched and first and second branched anal-fin rays, an unusual character in the Characidae.Among characids, bony hooks on pelvic-fin rays in females have been recorded only for the species of the genus Cheirodon Girard, 1855, in which they are considered a synapomorphic character by Malabarba (1998).According to that author, those bony hooks are not as developed in size as those of males, and sometimes they are visible only in large females, as is the case in A. jordanensis.Bony hooks on fins, longer pectoral-and pelvic-fin rays, straight shape of anal-fin profile, and smaller body sizes are secondary sexual dimorphic characters usually reported for males in the genus Astyanax.The presence of bony hooks in females of A. jordanensis might have several causes: masculinization, a natural endocrine variation, or it could be considered an autapomorphic character for this species.However, more detailed studies are needed in order to corroborate any of these alternative hypotheses.Previously, no other Astyanax has been described with bony hooks on anal-fin rays in females.

Table 1 .
Morphometric data of Astyanax jordanensis based on the holotype and paratypes.N = number of specimens analyzed, including holotype, SD = standard deviation, m = male, f = female.